The prior art has disclosed otoscopy, tympanometry, audiometry, laser Doppler vibrometry (LDV) and radiological imaging as methods for non-surgical examination of impaired hearing in a patient. Otoscopy involves an evaluation of the eardrum by a treating physician. However, it has the disadvantage that, on the one hand, it permits only a view of the eardrum and, on the other hand, it entails a purely subjective assessment by the physician. By contrast, in tympanometry, audiometry and other acoustic methods, the hearing ability or the impedance/compliance is measured, but only integral statements concerning the whole of the middle ear are possible. By contrast, an isolated assessment of the eardrum alone is not possible or is possible only with difficulty. Laser Doppler vibrometry is based on the frequency-resolved measurement of the vibration of the eardrum, but only at a single point of the eardrum. Corresponding devices for carrying out the aforementioned methods are disclosed, for example, in the documents WO 00/64 328 A1 and US 2008/0 262 314 A1.
To improve the early and reliable diagnosis of various pathologies, such as otitis media and tympanic effusion, and the locating of sound conduction disturbances, a spatially resolved and three-dimensional measurement of the structure of the human eardrum is desirable. A method by which this aim can be achieved is optical coherence tomography (OCT). This is a method which is known from the prior art and which permits contact-free, three-dimensional measurement of the structure of the human eardrum, in which method light from a broad-band, short-coherence light source is divided by a beam splitter into a sample beam and a reference beam, and the sample beam scattered on the eardrum to be examined is then superposed with the reference beam reflected on a mirror. The interfering beams are detected by spectral resolution. For example, in Fourier domain OCT, a depth profile of the reflectivity is calculated from an interference spectrum via Fourier transformation. To generate a three-dimensional image of the eardrum, the eardrum is scanned point by point in two lateral directions. An endoscope for carrying out the optical coherence tomography is known, for example, from the documents US 2013/0 060 131 A1, US 2009/0 185 191 A1 and U.S. Pat. No. 8,594,757 B2. With the extension to Doppler OCT, frequency-resolved measurements of the eardrum vibrations can be carried out in the context of an in vivo examination. As an alternative to frequency domain OCT, it is also possible to use time domain OCT or parallel or full-field OCT and further methods.